Meanwhile Congress, at the instance of John Dickinson of Pennsylvania and John Jay of New York, decided to try the effect of one more candid statement of affairs, in the form of a petition to the king. This paper reached London on the 14th of August, but the king refused to receive it, although it was signed by the delegates as separate individuals and not as members of an unauthorized or revolutionary body. His only answer was a proclamation dated August 23, in which he called for volunteers to aid in putting down the rebellion in America. At the same time he opened negotiations with the landgrave of Hesse-Cassel, the duke of Brunswick, and other petty German princes, and succeeded in hiring 20,000 troops to be sent to fight against his American subjects. When the news of this reached America it produced a profound effect. Perhaps nothing done in that year went so far toward destroying the lingering sentiment of loyalty. [Sidenote: Americans invade Canada, Aug., 1775--June, 1776.] In the spring Congress had hesitated about encouraging offensive operations. In the course of the summer it was ascertained that the governor of Canada, Sir Guy Carleton, was planning an invasion of northern New York and hoping to obtain the coöperation of the Six Nations and the Tories of the Mohawk valley. Congress accordingly decided to forestall him by invading Canada. Two lines of invasion were adopted. Montgomery descended Lake Champlain with 2000 men, and after a campaign of two months captured Montreal on the 12th of November. At the same time Benedict Arnold and Daniel Morgan set out from Cambridge with 1200 men, and made their way through the wilderness of Maine, up the valley of the Kennebec and down that of the Chaudière, coming out upon the St. Lawrence opposite Quebec on the 13th of November. This long march through the primeval forest and over rugged and trackless mountains was one of the most remarkable exploits of the war. It cost the lives of 200 men, but besides this the rear-guard gave out and went back to Cambridge, so that when Arnold reached Quebec he had only 700 men, too few for an attack upon the town. After Montgomery joined him, it was decided to carry the works by storm, but in the unsuccessful assault on December 31, Montgomery was killed, Arnold disabled, and Morgan taken prisoner. During the winter Carleton was reinforced until he was able to recapture Montreal. The Americans were gradually driven back, and by June, 1776, had retreated to Crown Point. Carleton then resumed his preparations for invading New York. [Sidenote: Washington takes Boston, March 17, 1776.]